From: Hal Murray <hmurray@megapathdsl.net>

Hi Hal, With a 20 bit DAC, even a small aging rate is going to show up.  I'll let the one GPSDO cook for a month or so and see what it shows then.  I'll also pull the data from the log file and see if I can see any correlation between the temperature and the EFC over time.  IOW, for data points separated by 3.5 days, does the temperature difference between the two point seem to play a large part of the change in the recorded DAC value. The graph was made from the logging data sent to the PC.  But, the firmware doesn't have access to historical data on the PC, so something is needed for aging calculations.  Tom mentioned here recently about the 58503A GPSDO saving 64 hours of data for it's aging calculations.  So, I just added a few hours to that to get to 3.5 days of history in the GPSDO. Bob ----------------------------------------------------------------- AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Hal Murray <hmurray@megapathdsl.net> To: Bob Stewart <bob@evoria.net> Cc: Hal Murray <hmurray@megapathdsl.net> Sent: Saturday, November 5, 2016 6:23 PM Subject: Re: [time-nuts] Thermal impact on OCXO > The OCXO has been hot for a number of months. Then I don't understand why it is still aging that much. > I changed the firmware to save the DAC voltage every 30 minutes for 3.5 > day That's not very long. How did you make the graph?  You had to get the data out to a place where you can plot it somehow.  If you can do that, why are you "saving" the data?  I assume you have a serial port to a PC or something like that. > The fuzz in the temperature line is, indeed, the HVAC cycling You could try putting a box over the unit to see if that slows down the temperature changes. Mostly, you are trying to block air flow. -- These are my opinions.  I hate spam.

   From: Hal Murray <hmurray@megapathdsl.net>

...with a 20bit DAC, a suitable voltage reference for that DAC and an HP3458... On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <bob@evoria.net> wrote: > Hi Hal, > > With a 20 bit DAC, even a small aging rate is going to show up. I'll let the one GPSDO cook for a month or so and see what it shows then. I'll also pull the data from the log file and see if I can see any correlation between the temperature and the EFC over time. IOW, for data points separated by 3.5 days, does the temperature difference between the two point seem to play a large part of the change in the recorded DAC value. > > The graph was made from the logging data sent to the PC. But, the firmware doesn't have access to historical data on the PC, so something is needed for aging calculations. Tom mentioned here recently about the 58503A GPSDO saving 64 hours of data for it's aging calculations. So, I just added a few hours to that to get to 3.5 days of history in the GPSDO. > Bob ----------------------------------------------------------------- > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > > From: Hal Murray <hmurray@megapathdsl.net> > To: Bob Stewart <bob@evoria.net> > Cc: Hal Murray <hmurray@megapathdsl.net> > Sent: Saturday, November 5, 2016 6:23 PM > Subject: Re: [time-nuts] Thermal impact on OCXO > >> The OCXO has been hot for a number of months. > > Then I don't understand why it is still aging that much. > > >> I changed the firmware to save the DAC voltage every 30 minutes for 3.5 >> day > > That's not very long. > > How did you make the graph? You had to get the data out to a place where you > can plot it somehow. If you can do that, why are you "saving" the data? I > assume you have a serial port to a PC or something like that. > > >> The fuzz in the temperature line is, indeed, the HVAC cycling > > You could try putting a box over the unit to see if that slows down the > temperature changes. > > Mostly, you are trying to block air flow. > > > > -- > These are my opinions. I hate spam. > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

  From: Azelio Boriani <azelio.boriani@gmail.com>

This seems to be turning into a rabbit hole from which there can be no possible return.  With no evidence, you question my competence and cast aspersions on my testing methodology.  I give up.  Have a nice day. Bob ----------------------------------------------------------------- AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Azelio Boriani <azelio.boriani@gmail.com> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Sent: Saturday, November 5, 2016 7:02 PM Subject: Re: [time-nuts] Thermal impact on OCXO ...with a 20bit DAC, a suitable voltage reference for that DAC and an HP3458... On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <bob@evoria.net> wrote: > Hi Hal, > > With a 20 bit DAC, even a small aging rate is going to show up.  I'll let the one GPSDO cook for a month or so and see what it shows then.  I'll also pull the data from the log file and see if I can see any correlation between the temperature and the EFC over time.  IOW, for data points separated by 3.5 days, does the temperature difference between the two point seem to play a large part of the change in the recorded DAC value. > > The graph was made from the logging data sent to the PC.  But, the firmware doesn't have access to historical data on the PC, so something is needed for aging calculations.  Tom mentioned here recently about the 58503A GPSDO saving 64 hours of data for it's aging calculations.  So, I just added a few hours to that to get to 3.5 days of history in the GPSDO. > Bob ----------------------------------------------------------------- > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > >      From: Hal Murray <hmurray@megapathdsl.net> >  To: Bob Stewart <bob@evoria.net> > Cc: Hal Murray <hmurray@megapathdsl.net> >  Sent: Saturday, November 5, 2016 6:23 PM >  Subject: Re: [time-nuts] Thermal impact on OCXO > >> The OCXO has been hot for a number of months. > > Then I don't understand why it is still aging that much. > > >> I changed the firmware to save the DAC voltage every 30 minutes for 3.5 >> day > > That's not very long. > > How did you make the graph?  You had to get the data out to a place where you > can plot it somehow.  If you can do that, why are you "saving" the data?  I > assume you have a serial port to a PC or something like that. > > >> The fuzz in the temperature line is, indeed, the HVAC cycling > > You could try putting a box over the unit to see if that slows down the > temperature changes. > > Mostly, you are trying to block air flow. > > > > -- > These are my opinions.  I hate spam. > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.

 A DAC that does 100 ppm / C is a pretty typical part. 10 ppm / C is unusually good
 A “good” voltage reference might do 2 ppm / C
 A very typical room will swing around +/- 2C without much going on.
 Open the door in the room or open a window and 10C is not unusual. 
 Grabbing a normal banana plug with your fingers will give you > 10 uV, other thermocouples are running around
 A DAC with < 10 uV of noise in the 0.01 to 1 Hz region is unusually good

  From: Azelio Boriani <azelio.boriani@gmail.com>

   From: Hal Murray <hmurray@megapathdsl.net>

Hi 2^20 is roughly 1 ppm. It is about 5 uV on a 5V line or 2.5 uV on a 2.5 V EFC center. A DAC that does 100 ppm / C is a pretty typical part. 10 ppm / C is unusually good A “good” voltage reference might do 2 ppm / C A very typical room will swing around +/- 2C without much going on. Open the door in the room or open a window and 10C is not unusual. Grabbing a normal banana plug with your fingers will give you > 10 uV, other thermocouples are running around A DAC with < 10 uV of noise in the 0.01 to 1 Hz region is unusually good That’s just looking at the easy to measure part of the system. A few hundred uV delta on the PCB between the OCXO ground pin and “ground” from grabbing the OCXO is harder to measure, but also pretty typical. It sums right into the EFC line. It’s not a rabbit hole so much as the details of the design at the level you have chosen to look at. Bob > On Nov 5, 2016, at 8:10 PM, Bob Stewart <bob@evoria.net> wrote: > > This seems to be turning into a rabbit hole from which there can be no possible return. With no evidence, you question my competence and cast aspersions on my testing methodology. I give up. > > Have a nice day. > > Bob ----------------------------------------------------------------- > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > > From: Azelio Boriani <azelio.boriani@gmail.com> > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Sent: Saturday, November 5, 2016 7:02 PM > Subject: Re: [time-nuts] Thermal impact on OCXO > > ...with a 20bit DAC, a suitable voltage reference for that DAC and an HP3458... > > On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <bob@evoria.net> wrote: >> Hi Hal, >> >> With a 20 bit DAC, even a small aging rate is going to show up. I'll let the one GPSDO cook for a month or so and see what it shows then. I'll also pull the data from the log file and see if I can see any correlation between the temperature and the EFC over time. IOW, for data points separated by 3.5 days, does the temperature difference between the two point seem to play a large part of the change in the recorded DAC value. >> >> The graph was made from the logging data sent to the PC. But, the firmware doesn't have access to historical data on the PC, so something is needed for aging calculations. Tom mentioned here recently about the 58503A GPSDO saving 64 hours of data for it's aging calculations. So, I just added a few hours to that to get to 3.5 days of history in the GPSDO. >> Bob ----------------------------------------------------------------- >> AE6RV.com >> >> GFS GPSDO list: >> groups.yahoo.com/neo/groups/GFS-GPSDOs/info >> >> From: Hal Murray <hmurray@megapathdsl.net> >> To: Bob Stewart <bob@evoria.net> >> Cc: Hal Murray <hmurray@megapathdsl.net> >> Sent: Saturday, November 5, 2016 6:23 PM >> Subject: Re: [time-nuts] Thermal impact on OCXO >> >>> The OCXO has been hot for a number of months. >> >> Then I don't understand why it is still aging that much. >> >> >>> I changed the firmware to save the DAC voltage every 30 minutes for 3.5 >>> day >> >> That's not very long. >> >> How did you make the graph? You had to get the data out to a place where you >> can plot it somehow. If you can do that, why are you "saving" the data? I >> assume you have a serial port to a PC or something like that. >> >> >>> The fuzz in the temperature line is, indeed, the HVAC cycling >> >> You could try putting a box over the unit to see if that slows down the >> temperature changes. >> >> Mostly, you are trying to block air flow. >> >> >> >> -- >> These are my opinions. I hate spam. >> >> >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

  From: Bob Camp <kb8tq@n1k.org>

Hi Bob, But will any of the things you mentioned show up as a more or less linear march downhill at about 1 step per hour over the course of 7 days?  In fact, I think Dan's units show about the same -1 per hour, and he's had them running continuously for many months.  I believe you use these same OCXOs, Bob.  They're Trimble 34310-T units salvaged from China.  What's been your experience with them over the long run as far as aging is concerned? Bob ----------------------------------------------------------------- AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Bob Camp <kb8tq@n1k.org> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Sent: Saturday, November 5, 2016 7:37 PM Subject: Re: [time-nuts] Thermal impact on OCXO Hi 2^20 is roughly 1 ppm. It is about 5 uV on a 5V line or 2.5 uV on a 2.5 V EFC center.     A DAC that does 100 ppm / C is a pretty typical part. 10 ppm / C is unusually good     A “good” voltage reference might do 2 ppm / C     A very typical room will swing around +/- 2C without much going on.     Open the door in the room or open a window and 10C is not unusual.     Grabbing a normal banana plug with your fingers will give you > 10 uV, other thermocouples are running around     A DAC with < 10 uV of noise in the 0.01 to 1 Hz region is unusually good That’s just looking at the easy to measure part of the system. A few hundred uV delta on the PCB between the OCXO ground pin and “ground” from grabbing the OCXO is harder to measure, but also pretty typical. It sums right into the EFC line. It’s not a rabbit hole so much as the details of the design at the level you have chosen to look at. Bob > On Nov 5, 2016, at 8:10 PM, Bob Stewart <bob@evoria.net> wrote: > > This seems to be turning into a rabbit hole from which there can be no possible return.  With no evidence, you question my competence and cast aspersions on my testing methodology.  I give up.  > > Have a nice day. > > Bob ----------------------------------------------------------------- > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > >      From: Azelio Boriani <azelio.boriani@gmail.com> > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Sent: Saturday, November 5, 2016 7:02 PM > Subject: Re: [time-nuts] Thermal impact on OCXO > > ...with a 20bit DAC, a suitable voltage reference for that DAC and an HP3458... > > On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart <bob@evoria.net> wrote: >> Hi Hal, >> >> With a 20 bit DAC, even a small aging rate is going to show up.  I'll let the one GPSDO cook for a month or so and see what it shows then.  I'll also pull the data from the log file and see if I can see any correlation between the temperature and the EFC over time.  IOW, for data points separated by 3.5 days, does the temperature difference between the two point seem to play a large part of the change in the recorded DAC value. >> >> The graph was made from the logging data sent to the PC.  But, the firmware doesn't have access to historical data on the PC, so something is needed for aging calculations.  Tom mentioned here recently about the 58503A GPSDO saving 64 hours of data for it's aging calculations.  So, I just added a few hours to that to get to 3.5 days of history in the GPSDO. >> Bob ----------------------------------------------------------------- >> AE6RV.com >> >> GFS GPSDO list: >> groups.yahoo.com/neo/groups/GFS-GPSDOs/info >> >>      From: Hal Murray <hmurray@megapathdsl.net> >>  To: Bob Stewart <bob@evoria.net> >> Cc: Hal Murray <hmurray@megapathdsl.net> >>  Sent: Saturday, November 5, 2016 6:23 PM >>  Subject: Re: [time-nuts] Thermal impact on OCXO >> >>> The OCXO has been hot for a number of months. >> >> Then I don't understand why it is still aging that much. >> >> >>> I changed the firmware to save the DAC voltage every 30 minutes for 3.5 >>> day >> >> That's not very long. >> >> How did you make the graph?  You had to get the data out to a place where you >> can plot it somehow.  If you can do that, why are you "saving" the data?  I >> assume you have a serial port to a PC or something like that. >> >> >>> The fuzz in the temperature line is, indeed, the HVAC cycling >> >> You could try putting a box over the unit to see if that slows down the >> temperature changes. >> >> Mostly, you are trying to block air flow. >> >> >> >> -- >> These are my opinions.  I hate spam. >> >> >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.